Comment 53 for bug 358533

I use Kubuntu 11.04 64-bit with KDE 4.6.2, and this bug is 100% reproducible for me. I use small 3-d party tool to connect to l2tp VPN (http://code.google.com/p/vpnpptp/). Whenever the VPN drops, or when I hit "Disconnect" button, plasma freezes hardly - no application launching, no widgets activity. I still can use ALT+F2 to get Konsole (Dolphin can be started too, but is very slow) to do "sudo reboot" - this is the only way I'm aware of to get back to working machine. Command "kbuildsycoca4 && pkill plasma && kstart plasma-desktop" doesn't work for me - plasma gets killed but fails to start.
I should mention that I have experienced this same bug when disconnecting my 3G modem. I have seen this 3 or 4 times, but it isn't as stable as with l2tp vpn.
As someone suggested, I've ran
"sudo gdb --pid `pidof plasma-desktop`"
, then 'freezed' plasma, then ran
"bt"
I'm not sure this is the right way of dyagnozing, but here's what I've got:

#0 0x00007f4a605ecf03 in poll () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007f4a54fcf104 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007f4a54fcf639 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3 0x00007f4a5d7fb3ef in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#4 0x00007f4a5cc38dfe in ?? () from /usr/lib/libQtGui.so.4
#5 0x00007f4a5d7cf882 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#6 0x00007f4a5d7cfabc in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#7 0x00007f4a5d7d3ecb in QCoreApplication::exec() () from /usr/lib/libQtCore.so.4
#8 0x00007f4a608e6897 in kdemain () from /usr/lib/kde4/libkdeinit/libkdeinit4_plasma-desktop.so
#9 0x00007f4a60532eff in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#10 0x0000000000400669 in _start ()

If I can provide any more detailed stacktraces, please let me know - this bug is really annoying and I will provide any help with it. Unfortunatly I'm java programmer, not C++, otherwise I would volunteer with the fix.